invoke.texi: Document -Wcast-function-type.

gcc:
2017-12-14  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        * doc/invoke.texi: Document -Wcast-function-type.
        * recog.h (stored_funcptr): Change signature.
        * tree-dump.c (dump_node): Avoid warning.
        * typed-splay-tree.h (typed_splay_tree): Avoid warning.

libcpp:
2017-12-14  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        * internal.h (maybe_print_line): Change signature.

c-family:
2017-12-14  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        * c.opt (Wcast-function-type): New warning option.
        * c-lex.c (get_fileinfo): Avoid warning.
        * c-ppoutput.c (scan_translation_unit_directives_only): Remove cast.

c:
2017-12-14  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        * c-typeck.c (c_safe_arg_type_equiv_p,
        c_safe_function_type_cast_p): New function.
        (build_c_cast): Implement -Wcast-function-type.

cp:
2017-12-14  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        * decl2.c (start_static_storage_duration_function): Avoid warning.
        * typeck.c (cxx_safe_arg_type_equiv_p,
        cxx_safe_function_type_cast_p): New function.
        (build_reinterpret_cast_1): Implement -Wcast-function-type.

testsuite:
2017-12-14  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        * c-c++-common/Wcast-function-type.c: New test.
        * g++.dg/Wcast-function-type.C: New test.

From-SVN: r255661

2 files changed, 69 insertions, 0 deletions

diff --git a/gcc/c/ChangeLog b/gcc/c/ChangeLog
index 3f5414b..d486018 100644
--- a/gcc/c/ChangeLog
+++ b/gcc/c/ChangeLog
@@ -1,3 +1,9 @@
+2017-12-14  Bernd Edlinger  <bernd.edlinger@hotmail.de>
+
+	* c-typeck.c (c_safe_arg_type_equiv_p,
+	c_safe_function_type_cast_p): New function.
+	(build_c_cast): Implement -Wcast-function-type.
+
 2017-12-14  Richard Biener  <rguenther@suse.de>
 
 	PR c/83415
diff --git a/gcc/c/c-typeck.c b/gcc/c/c-typeck.c
index 13b2684..541fb61 100644
--- a/gcc/c/c-typeck.c
+++ b/gcc/c/c-typeck.c
@@ -5472,6 +5472,59 @@ handle_warn_cast_qual (location_t loc, tree type, tree otype)
   while (TREE_CODE (in_type) == POINTER_TYPE);
 }
 
+/* Heuristic check if two parameter types can be considered ABI-equivalent.  */
+
+static bool
+c_safe_arg_type_equiv_p (tree t1, tree t2)
+{
+  t1 = TYPE_MAIN_VARIANT (t1);
+  t2 = TYPE_MAIN_VARIANT (t2);
+
+  if (TREE_CODE (t1) == POINTER_TYPE
+      && TREE_CODE (t2) == POINTER_TYPE)
+    return true;
+
+  /* The signedness of the parameter matters only when an integral
+     type smaller than int is promoted to int, otherwise only the
+     precision of the parameter matters.
+     This check should make sure that the callee does not see
+     undefined values in argument registers.  */
+  if (INTEGRAL_TYPE_P (t1)
+      && INTEGRAL_TYPE_P (t2)
+      && TYPE_PRECISION (t1) == TYPE_PRECISION (t2)
+      && (TYPE_UNSIGNED (t1) == TYPE_UNSIGNED (t2)
+	  || !targetm.calls.promote_prototypes (NULL_TREE)
+	  || TYPE_PRECISION (t1) >= TYPE_PRECISION (integer_type_node)))
+    return true;
+
+  return comptypes (t1, t2);
+}
+
+/* Check if a type cast between two function types can be considered safe.  */
+
+static bool
+c_safe_function_type_cast_p (tree t1, tree t2)
+{
+  if (TREE_TYPE (t1) == void_type_node &&
+      TYPE_ARG_TYPES (t1) == void_list_node)
+    return true;
+
+  if (TREE_TYPE (t2) == void_type_node &&
+      TYPE_ARG_TYPES (t2) == void_list_node)
+    return true;
+
+  if (!c_safe_arg_type_equiv_p (TREE_TYPE (t1), TREE_TYPE (t2)))
+    return false;
+
+  for (t1 = TYPE_ARG_TYPES (t1), t2 = TYPE_ARG_TYPES (t2);
+       t1 && t2;
+       t1 = TREE_CHAIN (t1), t2 = TREE_CHAIN (t2))
+    if (!c_safe_arg_type_equiv_p (TREE_VALUE (t1), TREE_VALUE (t2)))
+      return false;
+
+  return true;
+}
+
 /* Build an expression representing a cast to type TYPE of expression EXPR.
    LOC is the location of the cast-- typically the open paren of the cast.  */
 
@@ -5665,6 +5718,16 @@ build_c_cast (location_t loc, tree type, tree expr)
 	pedwarn (loc, OPT_Wpedantic, "ISO C forbids "
 		 "conversion of object pointer to function pointer type");
 
+      if (TREE_CODE (type) == POINTER_TYPE
+	  && TREE_CODE (otype) == POINTER_TYPE
+	  && TREE_CODE (TREE_TYPE (type)) == FUNCTION_TYPE
+	  && TREE_CODE (TREE_TYPE (otype)) == FUNCTION_TYPE
+	  && !c_safe_function_type_cast_p (TREE_TYPE (type),
+					   TREE_TYPE (otype)))
+	warning_at (loc, OPT_Wcast_function_type,
+		    "cast between incompatible function types"
+		    " from %qT to %qT", otype, type);
+
       ovalue = value;
       value = convert (type, value);